#startExamBtn
    {
      padding: 20px 30px;
      background-color: #4CAF50;
      color: white;
      border: none;
      cursor: pointer;
      font-size: 16px;
      width: 200px; 
      margin: 0 auto; 
      overflow: hidden;
      display: grid;
      justify-items: center;
    }
    body {
      font-family: Arial, sans-serif;
    }

 .container {
      width: 80%;
      margin: 0 auto;
    }

 .waiting {
      background-color: lightgray;
      padding: 20px;
      text-align: center;
    }

 .exam {
      background-color: white;
      padding: 20px;
      display: none;
    }

 .finished {
      background-color: lightgreen;
      padding: 20px;
      text-align: center;
      display: none;
    }

 .countdown-panel {
      position: absolute;
      top: 0;
      right: 0;
      background-color: rgba(0, 0, 0, 0.7);
      color: white;
      padding: 10px;
      border-radius: 5px;
    }